High Speed Synchronous Power
MOSFET Smart Driver
POWER MANAGEMENT
Description
The SC1405B is a Dual-MOSFET Driver with an internal
Overlap Protection Circuit to prevent shoot-through. Each
driver is capable of driving a 3000pF load in 15ns rise/
fall time and has ULTRA-LOW propagation delay from in-
put transition to the gate of the power FET’s. Adaptive
Overlap Protection circuit ensures that the synchronous
FET does not turn on until the top FET source has reached
a voltage low enough to prevent shoot-through. The de-
lay between the bottom gate going low to the top gate
transitioning high is externally programmable via a ca-
pacitor to minimize dead time. The bottom FET may be
disabled at light loads by keeping S_MOD low to trigger
asynchronous operation, thus saving the bottom FET’s
gate drive current and inductor ripple current. An inter-
nal voltage reference allows threshold adjustment for
an Output Over-Voltage protection circuitry, independent
of the PWM controller.
Under-Voltage-Lock-Out circuit is included to guarantee
that both driver outputs are off when Vcc is less than or
equal to 4.4V (typ) at supply ramp up (4.35V at supply
ramp down). A CMOS output provides status indication
of the 5V supply. A low enable input places the IC in stand-
by mode, reducing supply current to less than 10µA.
SC1405B is offered in a high pitch (.025” lead spacing)
TSSOP package.
SC1405B
Features
Fast rise and fall times (15ns with 3000pf load)
14ns max. Propagation delay (BG going low)
Adaptive and programmable shoot-through
protection
Wide input voltage range (4.5-25V)
Power saving asynchronous mode control
Output overvoltage protection/overtemp shutdown
Under-Voltage lock-out and power ready signal
Less than 10µA stand-by current (EN=low)
Improved drive version of SC1405TS
High frequency (to 1.2MHz) operation allows use of
small inductors and low cost capacitors in place of
electrolytics
Applications
High Density/Fast transient microprocessor power
supplies
Motor Drives/Class-D amps
High efficiency portable computers
Typical Application Circuit
INPUT POWER, 5-20V
+
Vcc
10uF,6.3V
+
.1uF
8
3
<<
>>
P_READY
PWM IN
(20KHz-1MHz)
47pF
7
2
4
6
1
5
14
13
12
SC1405
9
11
10
2.2
2.2
MTB75N03
75A,30V
5817
.22uF
1.7V@30A
+
+
+
+
+
MTB75N03
75A,30V
<<
DSPS_DR
Over-Voltage Sense
<<< Output Feedback to PWM
Controller
Revision: January 13, 2004
1
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